The disclosure relates generally to acoustic attenuation, and more particularly, to a silencer panel and system including an enclosure having at least one plastic perforated side wall and an electrostatic particle removal system.
Noise reduction systems are used on a large variety of industrial machines such as turbomachines to reduce the acoustic impact to surrounding areas. In gas turbine systems, for example, noise reduction systems may be employed in the inlet duct, gas turbine enclosures and barrier walls. Traditionally, to attain the necessary acoustic reduction requirements, silencer panels and/or acoustically treated walls are used in the noisy areas. One mechanism to reduce acoustic impact is to treat walls with acoustic absorbing material. Another mechanism is to place silencer panels in areas where noise reduction is required to contain the acoustical energy, such as a working fluid flow path in an intake system duct to prevent noise escaping.
With regard to silencer panels, each panel typically includes an acoustic absorbing material such as mineral/glass wool wrapped with fiber glass cloth positioned by a metal supporting member and surrounded by an enclosure including stainless steel perforated sheets on the sides thereof. The sheets are held together by stainless steel end caps. The stainless steel perforated sheets are typically welded to the supporting members that hold the acoustic absorbing material. The perforated stainless steel sheets hold the acoustic absorbing material intact with the supporting members and propagate the sound waves through the perforations into the acoustic absorbing material. Use of stainless steel enclosures presents a number of challenges. For example, the enclosures are very heavy, and are also difficult and costly to manufacture due to the cost of the material and the need for welding to form the panels. In addition, the steel construction must be welded in place to the surrounding duct and must be custom fit for a particular sized duct.
Another challenge for certain industrial machines, such as gas turbines, is ensuring particle removal from incoming working fluids, e.g., air. For example, advanced gas turbines are using higher firing temperatures to achieve higher performance. Here, particle removal from the working fluid is desired to reduce particle build up, such as calcium magnesium-aluminosilicate (CMAS) build up, and more readily achieve and maintain the higher firing temperatures. Electrostatic particle removal has been employed in a variety of settings to remove particles from working fluids. Previously, however, use of this form of particle removal with all metal noise reduction systems employing silencer panels has not been feasible because the electrostatic discharge is shorted by the metal enclosures, and/or particle build up on the silencer panels diminishes and/or eliminates acoustic absorption by the panels.